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Recently, it is demonstrated by our research group that the non-thermal plasma produced using the nano-second pulsed discharge has extremely higher energy efficiency to produce of ozone. On the other hand, the maximum ozone concentration has been saturated at approximately 40 to 50 g/m3. Therefore, for waste water treatments, the ns pulsed discharge based ozonizer still needs to have the higher ozone concentration around 120 g/m3. In this work, since many researchers reported that gas temperature in ozonizers strongly affects the characterization of the ozone generation, the gas temperature inside of the ozone generation reactor was experimentally measured to investigate the relationship between saturation of ozone concentration and gas heating. Additionally, the percentage of input energy lost as heating was investigated. As a result, the gas temperature inside the reactor was increased up to 313 to 323 K from room temperature. However, rise in gas temperature seemed to have little effect on the saturation of the ozone concentration at that temperature level. Also, in actually, 80 to 90% of input energy into the discharge reactor was used to heat the gas in and the metal electrode of reactor during the ns pulsed discharge. [ABSTRACT FROM PUBLISHER]

Pulsed discharges in atmospheric pressure gases have been studied for many years since it is one of the promising technologies for the removal of the hazardous environmental pollutants and ozone generation. In the literatures, especially, some researchers reported that an effect of pulse polarity on pollutants treatment. These experimental results indicate that the negative pulsed discharge gives an improvement of an energy efficiency of pollutant gas treatment. It is described that the polarity effect of pulsed discharge caused by difference of streamer propagation mechanism between both pulse polarities. However, no comparison results of the polarity effect in nanoseconds range pulsed discharge has been reported so far. In this paper, an investigation of the ozone generation using positive and negative nano-seconds pulsed discharges was conducted. In the experiments, ns pulse generator which has 5 ns of pulse duration in output pulsed voltage is employed. The results showed negative voltage polarity has higher ozone production yield than positive one at high voltage application. [ABSTRACT FROM PUBLISHER]

Pulsed streamer discharge plasma which is one of the non-thermal plasmas has been used to generate ozone and to treat exhaust gases. In our previous studies, it is found that a pulse duration of applied voltage has a strong influence on the energy efficiency of exhaust gas treatment and ozone generation. Therefore the development of a shorter pulse generator is of paramount importance for practical applications. The higher yield ozone generation and higher efficiency exhaust gas treatment using the developed nano-seconds (ns) pulsed generator having 5 ns of duration have been demonstrated. In this work, toluene decomposition using ns pulsed generator were investigated. The dependence of toluene removal ratio on ambient gases which are nitrogen, air, and oxygen and its by-products identification were carried out. As the results, the toluene removal ratio reach the highest in case of oxygen ambient gas, and in case of all of ambient gases, carbon monoxide, carbon dioxide, and formic acid were generated as by-products. In the dependence of toluene removal ratio on the peak of applied voltage, toluene removal ratio increased with its increasing the peak of applied voltage. In the case of 50 kV of applied voltage with air ambient gas, all of toluene molecules were decomposed. [ABSTRACT FROM PUBLISHER]

A ns pulse voltage was used to drive a coaxial geometry corona reactor to synthesis ozone with high energy yield. The ns pulse voltage was produced using an inductive energy storage system pulsed power generator using semiconductor opening switch (SOS) diodes. First recovery diodes were used as SOS diodes in the inductive energy storage system pulsed power generator to produce short-pulse high voltage with high-repetition rate. The pulse voltage of 12 ns width and 17 kV peak voltage was produced at charging voltage of −5 kV and was applied to a 1 mm diameter center wire electrode in the coaxial geometry reactor. The copper cylinder of 19 mm inner diameter was used as outer electrode and was connected to a ground. The ozone yield of 230 g/kWh was obtained using ns narrow pulse voltage. This value is almost 20% higher than 190 g/kWh obtained by 60 ns width pulse. [ABSTRACT FROM PUBLISHER]

Non-thermal plasma has been widely used in many applications, such as ozone generation, control of NOx and SOx from exhaust gases, dioxin decomposition, volatile organic compounds (VOCs) removal and laser excitation. Recently, it is demonstrated by our research group that the non-thermal plasma produced using the nano-seconds pulsed discharge has higher energy efficiencies of ozone generation and removal of pollutants in gases. However, the physical characteristics of nano-seconds pulsed streamer discharge is still not clear enough. In this paper, the axial propagations of nano-seconds pulsed discharge in a coaxial reactor were investigated by observing its streak images. In the results, influence of applied voltages and feeding gas composition against nano-seconds pulsed discharge propagation velocity are reported. [ABSTRACT FROM PUBLISHER]